Aluminum-base alloy and method of treating it



Patente Oct. 30, 1923.

I'QVNITED STATES Runner's. Aacima AND za Y mrrams, or CLEVELAND, omo, ASSIGNOBS 'ro nLU- MINUM COMPANY OF AMERICA, OF PITTSBURGH, PENNSYLVANIA, A. UUBPDM;

axon or PENNSYLVANIA.

ALUMINUM-BASE ALLOY m1) METHOD OF TBEATIH No Drawing.

To all whom it may concern:

Be it known that we, ROBERT S. ARCHER and ZAY Jnrrnms, citizens of the United States, and residents of Cleveland, in'the- The object of this invention. is to provide an aluminum base alloy, which, after having been worked and quenched is relatively soft and workable and remains so for an indefinite period when maintained at room temperature, and which, when subsequently artificially aged above room temperature,

possesses advantageous physical properties. vA, further object is to provide a method of treating certain worked aluminum base alloys so that they may be readily shaped or worked at any time and subsequentlyhave improved hysical properties.

Aluminum base alloys containing various constituents in diiferent percentages are known, and some of them have been commerciall used for some time. Also it is, old in t e art to quench some of these al loys from certain temperatures and to age them either naturally or artificially, that is to sa either at room temperatures or at.

elevate temperatures for the purpose'of improving their physical properties. For example a t pical composition of such a commercial a uminum base alloy is one consisting of 4% copper, 0.5% magnesium and 0.5% manganese, the remainder being commercial aluminum containing small percentages of various elements as impurities. When quenched according to standard practice this alloy has a tensile strength of about 40,000 to 45,000 lbs. per square inch, and an elongation of 20% and upwards in two .inches. After being quenched the alloy gradually ages at ordinary room temperatures until at the end of about four days its tensile strength may be 55,000 to 60,000 lbs. per square inch, especially in thin sheets. Itselongation is usually not greatly affected, but may either be increase or decreased. However, its plasticity or workability isidecreased by the aging.

Our invention is predicated upon our dis covery that a worked aluminum base alloy Application flled Deceinber 20,1921. Serial No. 523,890.

' uent time c artificially agedto producei ifi'erent physical properties.

In the practice of the invention copper alone may be the alloying element, or other elements such as manganese, chromium, sili-' con, and zinc may be added. The choice of a particular composition is governed largely by the use to which the articles made of it are put. If it is desired to obtain an easily workable alloy havin reasonably good physical properties, 1; ecopper content should be in the neighborhood of from about 3.5 to 4.5%. If high strength and hardness are to be obtained it is desirable to have a high copper content in some cases as high as 5.0%, and also to have manganese or chromium present in small quantities, preferably not exceeding about 1.0%,- and silicon resent in amount not exceeding about 1.0%.

, n such an alloy thephysical properties are obtained at some sacrifice of working pro erties, especially the breaking down of t e' r. The quenching temperature oi the alloy may vary according to the amount and char actor of the alloy constituents present. In

all cases, however, the best results are obtained when the alloy has been quenched from the temperature at which as much as possible of the copper and other alloying elemlents have gone into solution in the aluminum. By way of example, if the copper content is about et.5% or more, the quenching temperatur should not exceed about 540 C. for the best results. The

lower the copper content the higher isthe will as temperature and which may at any sub ermissible temperaturefr'om" which the aloy may be quenched without-injury, and the lower is the temperature at which maximum or nearly maximum physicalproperties can ultimately be' produced. For example, an allo containiiig about 3.5% copand readily workable, and its physical properties remain unchanged, or substantially so, for an indefinite period, which is an important advantage when it is desired to press, stam or otherwise shape or form the alloy at a later time, in contra-distinction to naturally aging allo which must be worked, if at all, immediately after quench- 1n %y .varying the time and temperature of a 'ng, various combinations of strength and ardness may be produced which are intermediate between those of the metal as quenched and the highest obtainable b proper, aging. However, the alloys are pre erablyaged'at temperatures between about 100 and 175 C. When it is not desired to subject the alloy to cold working after quenching, it may be quenched to the desired artificial aging temperature, rather than to room temperature. When an alloy is aged at higher tem ratures, say about 200, the first effect is ardening, the hardness being somewhat less than that produced by agin at 150 C. Prolonged aging at 200 C. or ti tensile strength and hardness, and usually a reduction in the ductility of the alloy. However, useful alloys can be produced when aged at a temperature of 200 C. if the duration of the aging is not too long. The increase in hardness is more rapid the higher the aging temperature, although the maximum hardness or strength obtainable by aging at 200 C. is not as great as the maximum obtainable at 150 C.

The invention thus briefly described may be further explained and fully understood by reference to a few examples of the alloys We have produced and tested. Having reference first to aluminum base-alloys containing copper alone, other elements being present only as impurities, a worked alloy containing 3.78% copper, when quenched from a temperature of 530 C. had a tensile strength of 42,250 lbs. per square inch and an elongation of 24% in two inches. When aged for about twenty-four hours at 150 C.

it had a tensile strength of 50,300 lbs. per

' In its a)! quenched state the alloy is relatively soft ereabouts produces decreased 'tion of 25% in two inches. As showing the improved physical properties brought about by increasing the copper content,-an'alloy containin 4.06% copper, quenched from 530 C. a ter being heated at such temperature for onehour and then aged for twentytwo hours at a temperature of 150 0., had

a tensile strength of 55,300 lbs. per square inch and an elongation of 25% in two inches. Also an alloy containing 4.86% copper quenched from a temperature of 530 at which it was maintained for one-half hour and aged at 150 for sixteen hours had a about.530 C. maintained for one-half hour,

they had tensile strengths ranging from 40,000 to 43,700 lbs. per square inch and elongations of from 20 to 25% in two inches. As in the case of alloys containing copper alone, the physical properties of the alloys containing manganese as an added element do not change to any noticeable extent on aging at room temperature even for months. \Vhen aged at a temperature between-about to 130 C. their strengths increase markedly and their elongations may increase or decrease or remain practicallv unchanged. A forged alloy having a tensile strength of 55,000 lbs. per square inch and an elongation of 25% in two inches can be easily obtained by aging for twentyfour hours to fortyeight hours at a temperature slightly below 130 C., the hardness being increased at the same time. If the quenched alloy is aged at a temperature between about 130 and 175 C. for a period of about fifteen to twenty four hours, the, tensile strength may be about 60,000 lbs. per square inch, the elongation 18% in two inches, and, the Brinnell hardness number about 120.

As an example of the stability of this type of alloy after being quenched, we found that forged test bars of an alloy containing 4.68% copper and 0.68% chromium hada and an elongation of 24% in two inches immediately after quenching, while'other bars from the same ingot of the same alloy tested after aging a year at room temperature had, a] tensile strength of 47,000 lbs.

per square inch, and an elongation of 26% in two inches. Still other bars from the same ingot of the same alloy after artificial aging at 150 had a tensile strength varying-- between 55,000 and 59, 00 lbs; per,

square inch and an elongation of 20% in. two inches. I

The physical properties of the alloy we provide may be further improved by the addition of silicon in greater proportion than usually found as an impurity in good grade commercial aluminum ingots. The

silicon may be increased to a total of from about 0.5% to 1.0%. An alloy containing such an added percentageof silicon has increased tensile stren th both after-quenching and after artificial aging, and 1S relatively ductile especially when aged at from about 100 to 17 5 C. In the form of rolled sheets it has been found to have a tensile strength of more than 65,000 lbs. per square inch, and an elongation of more than 20% in two inches after haying been quenched from a temperature above 500 C, and aged at about 125 C. for forty eight hours.

As a'specific example of alloys containing copper, manganese and silicon, an alloy containing 3.5% co per, 0.93% manganese and 0.6% silicon, a ter having been quenched from a temperature of 530 C. had a tensile strength of 43,100 lbs. per square inch and an elon ation of 21% in two inches. When artificia the al oy had a tensile strength of 58,000 lbs. per square inch and an elon ation of 20%. in two inches. The preferre alloy, that is to say, the alloy capable of being given the best physical properties is one containing about 4.5% copper, 0.75% manganese and 0.75% silicon, quenched from a temperature offrom about 500 to 540- C. and aged at a tem erature of from about 100 to 175 C.

l e have found that an alloy containing. 3.95% copper, 1.22% iron and 0.31% silicon,

' the silicon being present in thi proportion .tion of 20% in two inches.

as a natural consequence of the manufac--- ture of the aluminum as distinguished from being intentionally added, develops a maximum tensile strength of 31,600 lbs. per square inch and "i111 elongationof 20.5% in two inches, after it has been quenched and artificially aged. It thus appears that the relatively large percentage of iron present in the alloy decreases the maximum strength obtainable. The same has been found to be true of calcium in the absence of magnesium. For example, an alloy containing 3.98% copper, 0.04% calcium, and 0.29% silicon, eveloped a maximum tensile strength of 32,100 lbs. per square inch with an elonga- However, we

' have found that the bad effects of iron may be largely, if not entirely, overcome by the addition of silicon, The silicon, shouldbe at least equal to, and preferably in excess of,

the iron content, and may be present in quantities up to about 5% without seriously impairing the good physical properties of the alloy. However, the cold-working propaged at 150 C. for twenty-two hours The addition of chromium to the alloy containing more than about 3.5% copper and free from magnesium is beneficial. F or example, an alloy in the form of rolled sheet thick containing 1.72% copper and 0.68% chromium had a. tensile strength of 64,100 lbs. per square inch and an elongation of 20% in two inches after having been quenched from a temperature of 530 C. and aged for twenty-two hours at 150 C.

Small amounts of zinc, say up to 5% may be present in the alloy without substantially altering its character, although, because of certain disadvantages incident to the pun poseful introduction of zinc, We prefer not to add it, but desire to point ut'that zinc may be present and that the invention is not limited to alloys free from it.

The alloys we provide have important ad vantages, some of which have been mentioned. The present commercial high strength aluminum alloys containing magnesium are dfiicult to work. In the first place, there is more trouble in breaking down the ingots, than in the alloys we provide. In the second place, after the worked commercial alloys have been quenched from a relatively high temperature, there is no known way of keeping them from aging spontaneously except b cooling them to a very low tempera. ture, or example, that of liquid air. As aconsequence thereof their hardenin and loss in plasticity are not under contro and there is substantially only one set of physical properties obtainable, namely, those arrived at after the alloys have completely aged, although these properties may be somewhat improved by artificial aging. As distinguished from this, the alloys which we provide remain soft and plastic at room temperature when quenched, and their strength and hardness may be increased by controlling the time and temperature of aging so that any degree of strength and hardness between that obtained immediately after quenching and the maximum obtainable by the most effective aging can be-imparted to articles made from the alloys. It is frequently necessary in the fabrication of certain article of worked aluminum base alloys to put them into finished shape by deform ing them at room temperature, as by pressin stamping, etc. In the present commercia alloys'it is generally necessary to ef-u feet thi Working within a few hours and 'sometimeswithin an hour after they are quenched because their aging at room tern are quenched, and at subsequent time I v the. articles can be aged to increase the hardnatural aging of the alloy. For example, if

magnesium-containing scrap be inadvertently used in the preparation. of the alloy,. traces of magnesium will be present in the final roduct, However, the use of. such material should be avoided if natural aging is to be entirely,'or substantially entirely I prevented.

We claim as our invention: I c '1. A worked and quenched aluminum base alloy having workable x i l roperties while maintained at room temperature, fr'ee from magnesium and containing not less than about 3.5% copper, the physical properties of the alloy being capable of variable improvement by aging Cthe. alloy at a temperature above about 100:

2 A workable aluminum basealloy free.

from magnesium and containing not 1cm than about-3.5% copper, the alloy havin been worked and subsequently quenche from a temperature above about 500 C., and having substantially fixed physical properties while maintained at room temperature, the physical properties of the alloy being capable of variable improvements by aging (the alloy at a temperature above about 100 3. An aluminum base alloy free from mag.- nesium andcontaining not lessthan about 3.5% copper, the alloy having been worked and subsequently quenched from a temperature above about. 500 0., and subsequently aged at a temperature above about 100 C.

4. An aluminum base alloy free from magnesium and containing not less than about 3.5% copper, the alloy having been worked and subsequently quenched from a temperature of from about 500 to 540 C. and subsequently .aged at a temperature 0% from about 120 to 160 C. 5. A worked and quenched workable aluminum base alloy having substantially fixed physical properties while maintained at room temperature, free from magnesium and containing manganese and not less than about 3.5% copper, the physical properties ofthe alloy being ca able of variable improvements by agingt e alloy at a tempera ture above about 100 C.

6-. A workable aluminum base alloy free from magnesium and containing manganese and not less than about 35% copper, the alloy having been worked and subsequently substantially quenched from a temperature above about 500 C., and having substantially fixed physical properties while maintained at room temperature, the ph sical roperties of the alloy being capableo varia le improvfe .ments by aging the alloyat atemperature, above about 100 C.

7. An! aluminum alloy 'f from g;

nesium and containing manganese up to about 1% and not lessgthanabout 3.5% 00 per, the alloy having-been workedand su sequentl quenched from a temperature above .a out-500 (1., and subse uently artificialy-agcdat a temperature a ove about 100 g 8. A- worked and quenched workable aluminum base alloy having substantially fixed physical. properties while maintained at room temperature, free from magnesium and containing copper, manganese and silicon, the hysical properties of the alloy being capa le of variable improvements by aging the alloy at a temperature above about havin subsequently quenclied from a temperature above about" (3., and having substantially fixedf physical properties while maintained at room tempgraturathe physical roperties of the alloy ing capable of varia le improvements by aging the alloy at a above about C.

temperature 10. An aluminum base alloy free from magnesium and containing manganese up to about 1%, silicon up to about 1%, and copper not less than about 3.5%, the alloy having been worked and subsequently quenched from a temperature "above about 500 C., and subsequently artificially aged at a temperature above about 100 C.

11. A worked and quenched workable aluminum base alloy having substantially fixed physical. properties while maintained" at room temperature, free from magnesium and containing about 4.5% copper and 0.75% manganese, the physical properties of the alloy being capable of variable improvements by aging the alloy at a temperature above about 100 C.

12. An aluminum base alloy free from' magneslum and containing about 4.5% cop per and 0.75% manganese, the alloy having been Worked and subsequently quenched from a temperature above about 500 0., and artifiqijally aged at a temperature above about 1000 4 13. A worked and quenched workable aluminum base alloy having substantially fixed physical properties while maintained at room temperature, free from magnesium and containing about 4.5% copper, 0.75%

incense manganese and. 075% silicon, the physical properties of the alloy being capable of variable improvement by temperature above about 100 (J.

14:. An aluminum base alloy free from magnesiumexcept as an impurity and containing about 4.5%copper, 0.75% manganose, and 0.75% silicon, the alloy having been worked and subsequently quenched from a temperature above about 500 C, and an tificially ageol at a temperature above about I 500 (3., thereby renolering the alloy capable of having its physical properties improveol at any time by artificial agin 1'2. The method of treating a worked aluminum base alloy free from magnesium aml containing manganese, silicon and not less than about 3.5% copper, which consists in quenching the alloy from a temperature above about 500 G, thereby rendering the alloy-capable of having its physical properties im roveol at any time by artificial aging.

18. "he method. of treating a worked aluminum base alloy free from magnesium and containing manganese up to about 1%, silicon up to about 1% anti copper not less than about 3.5%, which consists in quench ing the alloy from a. temperature above about 500 0., thereby rendering the-alloy capable of having its physical properties improved. at any time by artificial aging.

10. The method of treating a worked aluminum base alloy tree from magnesium ancl containing about l.5% copper and. about .7570 .manganese, which consists in quenchaging the alloy at a;

ing the cilia from a' ternperature above about 500?. thereby rendering the alloy capable of havin its physical properties improved. at any time by artificial aging.

20. The method of treating a worked aluminumbase alloy free from magnesium and containing not less than 3.5% copper,

which consists in quenching the alloy from a temptelrature aboiile about 500 C., and subseuen y aging t e allo at a tem erature bove about 100 C. y

21. The method of treating a worked aluminum base alloy free from magnesium ami containing not less than 3.5% copper, whlch consists 1n quenching the alloy from a temperature above about 500 C., and subseguently aging the alloy at a temperature of rom about 120 C. to 160 C.

22.- The method of treating a worked aluminum "base alloy free from magnesium and containing manganese and not less than about 3.55% copper, which consists in quenching the alloy from a temperature above about 500 0., and subsequently aging the alloy at a temperature above about 100 C.

23. The 'method of treating a Worked aluminum base alloy free from magnesium and containinw manganese and silicon and not less than a out 3.5% copperflvhich consists in quenching the alloy from a temperature above about 500 (1, and subsequently In testimony whereof, we hereunto sign our names.

' nonnu'r s. anonnn.

ZAY JEFFRIES.

lVitnesses:

B. Pinon, TnoMAs J. Donner.

aging (She alloy at a temperature above about I 

